It may be worth noting the higher CPU and lower GPU usage in Ghost Recon Wildlands with Meltdown/Spectre patches enabled, which may indicate TLB flushing is eating CPU cycles and bottlenecking the GPU in this scenario.

Dutch publication Nieuwe Rotterdamsche Courant reports that Intel offered to pay the researchers a USD $40,000 "reward" to allegedly get them to downplay the severity of the vulnerability, and backed their offer with an additional $80,000. The team politely refused both offers.

Intel’s benchmarks suggest only a marginal decrease in within some tasks while Zombieload mitigations are in place.
Within the company’s in-house testing, a Core i9 9900K with HyperThreading enabled drops 3% performance in WebXPRT 3 testing. At best, it gained 1% within SPECint_rate_base 2017 (1 copy) testing.

The full mitigation, which includes disabling hyper-threading, prevents information leakage across threads and when transitioning between kernel and user space, which is associated with the MDS vulnerabilities for both local and remote (web) attacks. Testing conducted by Apple in May 2019 showed as much as a 40 percent reduction in performance with tests that include multithreaded workloads and public benchmarks. Performance tests are conducted using specific Mac computers. Actual results will vary based on model, configuration, usage, and other factors.

The Intel systems all saw about 16% lower performance out-of-the-box now with these default mitigations and obviously even lower if disabling Hyper Threading for maximum security. The two AMD systems tested saw a 3% performance hit with the default mitigations. While there are minor differences between the systems to consider, the mitigation impact is enough to draw the Core i7 8700K much closer to the Ryzen 7 2700X and the Core i9 7980XE to the Threadripper 2990WX.

Single patch, to address a couple of CPU vulnerabilities, caused Intel's Core i9 9900K processor to take 2 to 11% longer to process image sets in these photogrammetry applications. This is not the first update that has addressed such weaknesses in modern CPUs, so I wouldn't be surprised if the overall impact from those cumulative patches is even bigger. Some applications might be affected even more heavily, while others could see little or no difference - and of course, different CPUs may be affected more or less with each discovered vulnerability and subsequent patch. I look forward to seeing if this performance drop on the 9900K (and related models) impacts what CPUs are the best for photogrammetry moving forward, and we will have articles covering that topic in the coming days.

Here are some benchmarks of a Lenovo ThinkPad with Core i7 Broadwell CPU looking at those mitigation costs, when using a Core i7 5600U with two physical cores plus Hyper Threading.
The default/out-of-the-box mitigations dropped the performance by 18% or 25% when disabling Hyper Threading.

When looking at the current costs of all mitigations to date combined, that's a 13% hit using the same set of benchmarks carried out for the recent Xeon/EPYC comparison a few days back. If also disabling Hyper Threading, it equates to about a 19% hit.